Grinding method



Oct. 11, 1966 s, G, BRADY ETAL 3,277,613

GRINDING METHOD Original Filecx Jan. 24, 1961 United States Patent O M 3,277,613 GRINDING METHOD Samuel G. Brady, Bloomfield Township, and Wilhelm Dralle, Detroit, Mich., assiguors to Michigan Tool Company, Detroit, Mich., a corporation of Delaware Original application Jan. 24, 1961, Ser. No. 84,539, now Patent No. 3,121,297, dated Feb. 18, 1964. Divided and this application Oct. 9, 1963, Ser. No. 321,724 Claims. (Cl. 51-281) This invention relates to a grinding method and more particularly to methods for grinding grooves or slots in workpiece interiors and this application is a division of our application Serial No, 84,539, filed January 24, 1961, now Patent No. 3,121,297, issued February 18, 1964.

The problem of grinding internal grooves in workpieces, for example, after such grooves have been machined and hardened, is serious because of the space limitations Within some workpieces as well as the necessity of providing grooves having various cross-sectional shapes.

It is a general object of the present invention to provide an improved method for grinding such grooves, especially those having a curved or arcuate shape, which will result in an increased productivity rate, improvement in quality and exibility in terms of shape and size of the grooves.

It is another object to provide an improved orbital grinding method which will substantially reduce the total time required for indexing a workpiece to different angular positions in order to grind all the grooves, as compared with conventional methods such as oscillatory grinding.

It is a further object to provide an improved grinding method of this nature which is adapted for faster cutting or grinding of the workpiece material as compared with oscillatory grinding.

It is another object to provide an improved grinding method having these characteristics, in which the surface nish roughness lines will be parallel with the grooves, thus decreasing frictional resistance as compared with methods producing transverse roughness lines.

It is also an object to provide an improved grinding method of this character which is reliable and efficient, and is capable of grinding to close tolerances on a con- -tinuous basis, being adapted to cooperate with wheel dressing means in a manner which will insure accurate grinding of the workpieces.

Other objects and advantages of the present invention will become apparent from -the subsequent description, taken in conjunction with the accompanying drawings.

In the drawings:

FIGURE l is a cross-sectional view in elevation of a typical workpiece of the type which may be ground using the novel method of this invention;

FIGURE 2 is an end view of the workpiece shown in FIGURE 1 with parts broken away, looking in the direction of the arrow 2 in FIGURE l;

FIGURE 3 is a fragmentary view similar to FIGURE 2 showing a different cross-sectional shape of the slots which may be ground according to the invention;

FIGURE 4 is a cross-sectional view of the workpiece shown in FIGURE 1 with the grinding wheel inserted therein, showing diagrammatically how the orbital method grinds two grooves in a workpiece simultaneously.

FIGURE 5 is a diagrammatic view showing the orbital method of the invention and the manner in which the grinding wheel is fed between passes.

In general terms, the illustrated embodiment of the invention is for the purpose of grinding a plurality of axially extending circumferentially spaced slots on the concave internal surface of a workpiece. In carrying out the invention, a grinding wheel rotating on an axis 37,277,613I Patented oct. 11, 1966 at right angles to the extent of the grooves is moved in a manner such that its axis describes circles of increasing diameter about a central point. Each circuit thus causes the grinding wheel to grind two oppositely disposed grooves. After these two grooves have been completely ground, the grinding Wheel is withdrawn from the workpiece and the latter is rotated to bring two more oppositely disposed grooves into grinding position.

Referring more particularly to the drawings, FIGURES l to 3 illustrate a typical workpiece with which the invention may be used. The workpiece is generally indicated at 11 and represents, for example, a universal joint element having a shaft portion 12 at one end and a hollow semi-spherical portion 13 at the other end, a locating surface 14 being disposed between these two portions. The internal surface 15 of portion 13 is to be provided with accurately dimensioned grooves 16, these grooves being of arcuate shape, concave inwardly, and extending from end surface 17 of the workpiece to an enlarged recess 18 within the workpiece.

As seen in FIGURE 2, six equidistantly spaced grooves 16 may be required so that the grooves may be divided into three pairs, the grooves of each pair being apart. The cross-sectional shape of each groove may be formed of a single arc, as shown in FIGURE 2, of two arcs as indicated at 19 in FIGURE 3, or of other shapes.

The principles of the invention are diagrammatically illustrated in FIGURES 4 and 5 in which a series of passes for fully grinding one pair of grooves 16 is illustrated. The line 21 extending between the letters X-X represents the central axis of shaft 12 of the workpiece. A grinding wheel 22 is provided, the outer edge of which has a cross-sectional shape complementary to the nal cross-sectional shape to be obtained in each groove 16. This grinding wheel is continuously rotated on a spindle axis at right angles to line 21 and at right angles to the plane of the paper in FIGURES 4 and 5.

A reference point 23 on line 21 is chosen such that grinding wheel 22 will be equally spaced from a pair of oppositely disposed grooves 16 when its axis is at point 23. That is, point 23 is at the common center of curvature of each pair of oppositely disposed grooves 16. The grinding wheel spindle is first placed at a point 24 on line 21 being spaced a preselected distance from point 23 toward recess 18.

With the grinding wheel continuing -to spin, its spindle is then moved on a clockwise circular path from point 24. When the spindle axis reaches a point 25 on a line 26 extending upwardly and to the left from point 23 in FIGURE 5, the grinding wheel will begin to grind the upper groove 16 in FIGURE 4. As the grinding Wheel continues its orbital movement, the upper groove 16 will be ground, the grinding wheel will leave this groove and will then begin to grind the lower groove 16. This will continue until the grinding wheel axis reaches the point 27 on a line 28 extending downwardly and to the left from point 23 in FIGURE 5. At this poin-t grinding wheel 22 will leave lower groove 16.

As the grinding wheel spindle continues its movement from line 28 to line 26, its radius of orbit will be increased until, when it arrives at line 26, the spindle axis will .be at point 29 in FIGURE 5. The grinding wheel will thus begin to take another cut in upper groove 16, the radius of orbit being maintained constant until line 28 is again reached, this point being indicated at 31. The orbital radius is then again increased so that when line 26 is reached, the spindle axis will be at point 32. A deeper cut will thus be taken in both grooves 16, and this process will continue until the iinal depth is reached.

When the spindle axis reaches point 33 on this final path, on line 28, a mechanical stop and limit switch will prevent further increase in the orbital radius, and when point 34 is reached on line 21,l the spindle axis will be retracted to the right until it is out of the workpiece. The latter may then be rotated on its own axis to align another pair of grooves with the grinding wheel.

The method described above may conveniently be performed by means of the apparatus described in the aforementioned patent application of which this application is a division. As is noted in that patent application, the grinding wheel 22 may make several complete orbits at its maximum radius to provide the desired surface finish upon the grooves 16. In addition, dressing of the grinding wheel 22 will necessitate an increase in the final orbital radius for the next successive groove.

While it will be apparent that the preferred embodiment herein iilustrated is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is: t

1. The method of grinding a surface comprising the steps of rotating a grinding Wheel about an axis disposed in a transverse plane to said surface, moving the grinding wheel in an orbital path and into engagement with the surface, continuing the orbital movement of the grinding wheel until the grinding wheel no longer engages the surface, altering the orbital radius when out of engagement with the surface, the alteration of the orbital radius of the grinding wheel taking place without contact of the grinding wheel with the surface for precluding the removal of any material during the change in orbital radius, and moving Ithe grinding wheel into re-engagement with the surface along the new orbital radius and after the grinding wheel is moving along the new orbital radius to remove further material from the* surface.

2. The method as set forth in claim 1 wherein, the successive orbital radii have the same center and are parallel to -the axis of rotation of the grinding wheel.

3. The method of grinding a pair of oppositely disposed surfaces comprising the steps of rotating a grinding wheel about an axis disposed in a transverse plane between said surfaces, moving the grinding wheel in an orbital path into movement with the tirst of -the surfaces, out of engagement with the rst surface and into engagement with the second surface, continuing the orbital movement of the grinding wheel until -the grinding wheel no longer engages either surface, alter-ing the orbital radius when out of engagement with the surfaces, and again moving the grinding wheel successively into engagement with the surfaces along the new orbital radius to remove further material from the surfaces.

4. The method as set forth in claim 3 wherein the successive orbital radii have the same center and are parallel to the axis of rotation of the grinding wheel.

5. The method as set forth in claim 4 wherein the grinding wheel is disposed between the surfaces and the orbital radius is successively increased.

References Cited by the Examiner UNITED STATES PATENTS 7/ 1923 Kottman 5 1 90 4/ 1962 Folley 51-33 

1. THE METHOD OF GRINDING A SURFACE COMPRISING THE STEPS OF ROTATING A GRINDING WHEEL ABOUT AN AXIS DISPOSED IN A TRANSVERSE PLANE TO SAID SURFACE, MOVING THE GRINDING WHEEL IN AN ORBITAL PATH AND INTO ENGAGEMENT WITH THE SURFACE, CONTINUING THE ORBITAL MOVEMENT OF THE GRINDING WHEEL UNTIL THE GRINDING WHEEL NO LONGER ENGAGES THE SURFACE, ALTERING THE ORBITAL RADIUS WHEN OUT OF ENGAGEMENT WITH THE SURFACE, THE ALTERATION OF THE ORBITAL RADIUS OF THE GRINDING WHEEL TAKING PLACE WITHOUT CONTACT OF THE GRIND- 